I think we all know that with chipmunk effect it is impossible to recognize anyone's voice, unless someone has superhuman ears.
The thing with the Cascio tracks, they don't seem to be sped up by 50%, but rather to be either slowed down or sped up by one, two or three percent or maybe more, but certainly not to the extent to make Michael's voice unrecognizable. Why would anyone use any tool to transform Michael's voice into something that he doesn't sound himself?
So I am sorry, but your argument gives impression that on the one hand you open the possibility that Michael is the singer on the Cascio tracks and on the other that the reason why some don't recognize him is because the melodyne can speed up the voice to the extent nobody can recognize it. But again, firstly the Cascio tracks aren't that processed. Secondly, they awfully sound not Michael. Thirdly, why do you always give impression to defend something untolerable such as those horrible tracks?
We've just seen from some posts here how "Stranger in Moscow" could be altered to the point to produce a completely new song which has nothing to do with the initial one. The Cascio tracks are even worse. Not only they sound completely unnatural, but also they don't have Michael's usual voice.